1. Field of the Invention
The present invention relates to a so-called energy-absorbing fastened structure, and more particularly to an energy-absorbing fastened structure of a reclining device which is installed on an automotive seat, the fastened structure being capable of preventing or at least minimizing damages upon an accident to a lock mechanism of the reclining device.
2. Description of the Prior Art
Hitherto, various kinds of reclining devices have been proposed and put into practical use particularly in the field of automotive seats. As is known, the reclining device serves to adjust angular position of a seatback of an automotive seat and to lock the same at a certain desired angular position relative to a seat cushion thereof to provide a seat occupant with a comfortable sitting posture.
For example, JP-A (Patent) 63-318911 discloses a reclining device having therein a planetary gear arrangement. This type of reclining device installed on a motor vehicle seat can steplessly adjust angular position of a seatback thereof and lock the same at a certain desired angular position relative to a seat cushion thereof. The reclining device comprises first and second supporting plates which are respectively formed with ring gears meshed with a plurality of planetary gears, a control gear which is meshed with the planetary gears and coaxially mounted on a control shaft, an arm plate which is secured to the seatback, and a base plate which is secured to the seat cushion. The first and second supporting plates are respectively secured to the arm plate and the base plate through connecting pins. Thus, when the control shaft is rotated, the first supporting plate and the arm plate are slowly rotated about an axis of the control shaft so as to adjust the angular position of the seatback. When rotation of the control shaft is stopped, the seatback is locked at a certain desired angle.
When, for example, the motor vehicle is hard rear-ended by another vehicle, a seat occupant of the vehicle is abruptly rearwardly forced to move relative to the seat and struck at his or her back onto the seatback. Therefore, a heavy shock load is added to the seatback and the reclining device which supports the same. Therefore, the reclining device can be strongly built so as to support the load and thus to prevent or at least minimize damages to the same. However, this increases the production cost of the reclining device.